Dynamic operation of flexgrid networks might cause optical spectrum to be divided into fragments, which makes it difficult finding contiguous spectrum of the required width for incoming connection requests, leading thus to an increased blocking probability. To alleviate to some extent that spectrum fragmentation, the central frequency of already established connections can be shifted to create wider contiguous spectrum fragments to be allocated to incoming connections; this procedure is called spectrum defragmentation. In this paper, we propose using the so called applications based network operations (ABNO) architecture, currently under standardization in the IETF, to deal with the defragmentation use case while the network is in operation. A work flow involving several elements in the ABNO architecture is proposed and experimentally assessed in a distributed test bed connecting facilities in three major European cities.